In the manufacture of an electronic device, a processing of forming an opening such as a hole or a trench may be performed in a region made of silicon oxide (SiO2) in some cases. In such a processing, a workpiece is generally exposed to plasma of a fluorocarbon gas so that the exposed region is etched, as described in Patent Document 1.
A technology for selectively etching a first region made of silicon oxide with respect to a second region made of silicon nitride has been known. As an example of such a technology, a self-aligned contact (SAC) technology has been known. The SAC technology is described in Patent Document 2.
A workpiece, which is a processing target of the SAC technology, includes a first region made of silicon oxide, a second region made of silicon nitride, and a mask. The second region is provided so as to define a recess, the first region is provided to fill the recess and cover the second region, and the mask is provided on the first region and provides an opening above the recess.
In the SAC technology in the related art, plasma of a processing gas containing a fluorocarbon gas, oxygen gas, and a rare gas is used to etch the first region, as described in Patent Document 2. By exposing the workpiece to the plasma of the processing gas, the first region is etched at the portion exposed from the opening of the mask so as to form an upper opening. In addition, since the workpiece is exposed to the plasma of the processing gas, a portion surrounded by the second region, that is, the first region in the recess, is etched in a self-aligning manner.
Thus, a lower opening continuous to the upper opening is formed in a self-aligning manner. In addition, when a deposit from the carbon-containing plasma gas included in the plasma gas is formed around the opening, the opening end face is protected, so that only the inside of the opening may be selectively etched.
In addition, as related technologies, a method of etching SiO2 using CHF-based gas plasma (Patent Document 3), a method of selectively etching silicon nitride using fluorohydrocarbon (CH3F, CH2F2), O2, and carbon gas (CO2) (Patent Document 4 and Patent Document 5), a method of forming a contact hole using fluorocarbon (Patent Document 6), a method of etching SiC using CH2F2 or CH3F (Patent Document 7), and the like have been known.